Sleep disordered breathing is common in patients with tetraplegia. Nocturnal arterial hypoxemia and sleep fragmentation due to sleep apnoea may be associated with cognitive dysfunction. We therefore studied the in¯uence of sleep disordered breathing on neuropsychological function in 37 representative tetraplegic patients (mean age 34+9.7 years). Thirty percent (11 of 37 patients) had clinically signi®cant sleep disordered breathing, de®ned as apnoea plus hypopnoea index (AHI) greater than 15 per hour of sleep. Most apnoeas were obstructive in type. Seven patients (19%) desaturated to 580% during the night. Neuropsychological variables were signi®cantly correlated with measures of sleep hypoxia, but not with the AHI and the frequency of sleep arousals. The neuropsychological functions most aected by nocturnal desaturation were: verbal attention and concentration, immediate and short-term memory, cognitive¯exibility, internal scanning and working memory. There appeared to be a weak association between the presence of severe sleep hypoxia and visual perception, attention and concentration but no association was found between sleep variables and depression scores. We concluded that sleep disordered breathing is common in patients with tetraplegia and may be accompanied with signi®cant oxygen desaturation. The latter impairs daytime cognitive function in these patients, particularly attention, concentration, memory and learning skills. Cognitive disturbances resulting from sleep apnoea might adversely aect rehabilitation in patients with tetraplegia.

The cognitive deficits associated with schizophrenia commonly include impairment in attention, which may contribute to difficulties with learning, memory, and executive function. This study evaluated the effectiveness of computer-aided training of attentional skills in schizophrenia. Two groups of schizophrenic subjects (9 men and 1 woman) were matched for age, estimated premorbid IQ, and positive and negative symptom scores. Both groups were assessed using a battery of attentional tests. Subjects then received either six 1-hr. computer-aided cognitive rehabilitation sessions (experimental condition) or six sessions of graphics-based computer games (control condition). Both groups were reassessed with attentional measures. There was significant improvement on only one test, a letter-cancellation task. This improvement was evident in both groups suggesting that this was a practise effect. Apart from the letter-cancellation test, subjects undertaking the computer-aided rehabilitation treatment did not show significant improvement on any attentional tasks.

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There is minimal clustering effect of quality of life in COPD patients between the hospitals studied. Despite this, when using a cluster randomised design the sample size needed to detect the same effect as a study using simple randomisation could be inflated by up to 183%. If cluster randomization is required, the average cluster size should be kept as small as possible to negate this effect.

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